This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Bacterial blood infection is a frequent and serious problem in neonatal intensive care units, particularly in very low birth weight infants. Diagnosis by blood culture is difficult, time consuming, and lacks sensitivity. Over 20% of all very low birth weight infants experience one or more episodes of late onset sepsis [defined as any sepsis occurring after 3 days of age]. The median age for the first episode of late onset sepsis is 17 days. Delaying treatment until symptoms arise can be life threatening. On the other hand, recurrent treatment with antimicrobial agents in infants that are not infected holds potential risks to these infants by furthering the development of resistant organisms. This therefore, is an ideal population to evaluate to develop a rapid and sensitive product to identify infection. Newborns [especially premature infants or those with very low birth weight] are at much greater risk for life-threatening infections than older children and adults. Diagnosing these infections is difficult with current laboratory methods. Because of the life-threatening nature of these infections, infants in the Newborn Intensive Care Unit [NICU] are almost always placed on powerful antibiotics until we can confirm whether or not an infection is truly present. While these medications are necessary, using them too frequently can cause germs to develop resistance, which prevents the antibiotics from being effective. The purpose of this research study is to investigate a new laboratory method of diagnosing infections in newborns using a single drop of blood. From this small amount of blood we can test for markers of infection. We will be looking for markers that would suggest that an infant is infected. We intend to compare these tests with current methods in order to find out if we can diagnose serious infections more quickly. This may allow us to avoid treating infants with antibiotics when they are not needed.